#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
int main()
{
    int a = 0;
    int b = 0;
    int c = 0;
    int d = 0;
    int f = 0;
    double aver = 0.0;
    scanf("%d %d %d %d %d", &a, &b, &c, &d, &f);
    aver = (a + b + c + d + f) / 5.0;
    printf("%.1f\n", aver);
    return 0;
}